PNP Powershell Script Document Library Inventory

Hi I am using this script to return all documents in a site collection. I have some custom columns in the library but I am unsure how to add them to the script, specifically the internal name. Is there a way to get all column names so that I can put them in the csv ?

#Connect to SPO
Connect-PnPOnline -Url “”
#Store in variable all the document libraries in the site
$DocLibrary = Get-PnPList | Where-Object { $_.BaseTemplate -eq 101 }
$LogFile = “C:users$env:USERNAMEDesktopSPOFolders.csv”
$results = @()
foreach ($DocLib in $DocLibrary) {
#Get list of all folders in the document library
$AllItems = Get-PnPListItem -PageSize 1000 -List $DocLib -Fields “SMTotalFileStreamSize”, “Author”

#Loop through each files/folders in the document library for folder size = 0
foreach ($Item in $AllItems) {
   # if ((((uint64)$Item("SMTotalFileStreamSize")) -eq 0)) {
        Write-Host "Empty folder:" $Item("FileLeafRef") -ForegroundColor Yellow

        #Creating object to export in .csv file
        $results += (pscustomobject)(ordered) @{
            CreatedDate      = (DateTime)$Item("Created_x0020_Date")
            FileName         = $Item("FileLeafRef") 
            CreatedBy        = $Item.FieldValues.Author.LookupValue
            ContentType      = $Item("ows_ContentType")
            FilePath         = $Item("FileRef")
            SizeInMB         = ($Item("SMTotalFileStreamSize") / 1KB).ToString("N")
            LastModifiedBy   = $Item.FieldValues.Editor.LookupValue
            EditorEmail      = $Item.FieldValues.Editor.Email
            LastModifiedDate = (DateTime)$Item("Modified")
            CaseManager      = $Item("Case_x0020_Manager").Email)
    }#end of IF statement

$results | Export-Csv -Path $LogFile -NoTypeInformation